It is the purpose of the research proposed here to examine the relationship between 13C and H1 nmr chemical shifts and coupling constants and the conformations of selected natural products. Compounds of rigid and known stereochemistry, e.g. steroids and bicyclic compounds, will be examined to determine the effects of conformation, configuration, and substituents on the spectra. Insight into the conformations of acyclic and cyclic molecules will be obtained using ytterbium and europium shift reagents for 13C and 1H spectra. We shall initiate 13C relaxation time studies to supplement these conformational studies. Systems to be examined include a wide variety of steroids, bicyclic compounds, decalin derivatives, folic acid, and some very highly hindered compounds. Examination of the interaction of C13 labelled folic acid with certain enzyme systems will be combined with attempts to obtain good C13 spectra of the enzymes as well. Specifically labelled compounds and compounds for substituent effect studies will be synthesized as needed.